The present invention relates generally to injection assemblies for soft tissue expander devices. Particularly, the invention relates to improvements to injection port assemblies for filling soft tissue expanding devices such as tissue expanders and mammary prosthesis. The injection assemblies utilize composite silicone materials having fiber mesh layers embedded therein. The composite materials of the invention may cover and/or extend from an injection port structure and which are constructed to self seal when punctured by a hypodermic filling needle, for example. The invention further relates to injection port structures constructed of MR safe and/or MR conditional materials to provide tissue expander structures safe for scanning by a Magnetic Resonance Imager (MRI), for example.
The present invention provides improved injection port and injection area assemblies for soft tissue expanders. The injection ports of the invention improve upon prior art injection port structures to thereby assist the user, e.g., medical technician, practitioner or physician, in performing various medical procedures related to tissue expanders and/or mammary prosthesis. For example, U.S. Pat. No. 6,743,254 ('254 Patent) describes a tissue expander with protection against accidental puncture, however, the '254 Patent discloses a silicone matrix which is swelled by exposure to dimethylpolysiloxane, adhered into a tissue expander and a hole is punched through this material to locate the injection port. The '254 Patent discloses a two piece design, which requires both a tolerance space in between the injection port and silicone matrix, as well as adhesion of the injection port on the external surface of the soft tissue expansion device. The '254 Patent two piece design could potentially allow a needle puncture in between the silicone matrix and the injection port assembly and requires the injection port assembly to extend past the soft tissue expansion device silicone shell in order to seal the device on the external surface during final device assembly.
Additionally, patent application publications No. US20110270391 and No. US20090118756 teach the use of silicone gel or other viscous fluid under compression to facilitate the closing of injection needle paths to effectively self-seal soft tissue expansion devices. The utilizing of silicone gel or other viscous fluid complicates the device assembly and increases the costs associated with manufacturing.
Further, prior art U.S. Pat. No. 4,685,447 teaches the use of a metal plate and x-ray procedure to locate an injection port and U.S. Pat. No. 6,588,432 discloses a tissue expander system that utilizes a magnet for locating an injection port located under the skin. Although the injection port structures of these patents have been proven useful, occasionally medical personnel will miss the intended injection location near the center of the injection port. The present invention increases the probability of a successful tissue expander filling procedure with a reduced probability of leakage caused by needles missing the injection port and puncturing the shell of the tissue expander and/or mammary prosthesis.
The present invention resolves potential issues relating to prior art structures, that utilize two piece designs, by integrating a silicone composite of Dacron® fibers, i.e., polyester fibers, and silicone rubber into a unitary injection port structure. The one piece unitary structure of the invention eliminates the possibility of a needle puncture in-between the port and protective silicone matrix. The present invention also protects the tissue expanding device from accidental needle puncture by a resealing characteristic which is achieved without the use of a swelling agent in the manufacturing process, such as described in the prior art '254 Patent. The unitary composite self sealing ring of the invention overcomes the shortcomings and limitations of the prior art.
The present invention reduces manufacturing costs and time required in patent application publications No. US20110270391 and No. US20090118756, as the present unitary self-sealing injection port does not need to encapsulate a low durometer silicone gel or viscous fluid layer within the self-sealing silicone composite to self-seal leak causing needle paths after an injection. The present invention utilizes two or more layers of polyester mesh, positioned at the correct depth and orientation, to effectively self-seal a composite silicone matrix material having a single durometer reading adhered within a soft tissue expansion device. The elimination of a silicone gel or viscous fluid layer within the silicone composite material is a desired improvement by reducing material costs and time associated with manufacturing.
The present invention further improves upon the limitation of prior art devices to thereby assist the user (e.g. medical technician, practitioner or physician) in performing various medical procedures related to the device. The invention resolves potential issues for the patient encountered by prior art injection port structures having ferrous or metallic parts, such as stainless steel or magnets, and which restrict the patient from having imaging performed with an MRI, which subjects the device to a magnetic resonance field. The tissue expander injection port configuration of the invention improves the device by replacing the components affected by the MR field created by a Magnetic Resonance Imager with MR scannable, i.e., MR safe and/or MR conditionally safe materials.
The terminology defined in ASTM F2503 and recognized by the FDA are as follows: MR safe: An item that poses no known hazards in all MR imaging environments. With this terminology, MR safe items are non-conducting, nonmetallic, and nonmagnetic items. MR conditional: An item that has been demonstrated to pose no known hazards in a specified MR environment with specified conditions of use. The materials utilized in this invention relate to implantable soft tissue expanders capable of being subjected to the magnetic fields resulting from MRI equipment used in medical environments. The biocompatible MR safe and/or MR conditional materials may include PEEK, HDPE, titanium and like materials. MR safe and/or MR conditional materials are referred herein collectively as MR scannable materials unless specifically referring to either as MR safe or MR conditional material.
A tissue expander and other inflatable and inplantable devices are typically injected using a hypodermic needle or similar device by filling the injection port which is in communication with the tissue expander. For example, Applicant assignee's prior art, U.S. Pat. No. 4,685,447 (Iversea et al.) teaches the use of a metal plate and an x-ray procedure to locate an injection port, and U.S. Pat. No. 6,588,432 (Rehder et al.) describes a tissue expander system that utilizes a magnet for locating the injection port under the skin. While these patents have proven to be useful for locating an injection port, they are not MR scannable devices. Subsequent implantation of an above referenced prior art device, the patient cannot and should not be exposed to the magnetic forces used by an MRI due to the use of metallic and magnetic parts within the injection port structures. The present invention allows a tissue expander or similar inflatable device to be injected with a saline or similar fluid, using a hypodermic needle or similar device, without restricting the patient's access to high strength magnetic fields, such as being scanned by an MRI after the device has been implanted.